Phoenix, Arizona - President-elect Donald Trump on Sunday played down suggestions that far-right billionaire Elon Musk could one day take over from him.

"He's not gonna be president, that I can tell you," Trump told a Republican conference in Phoenix, Arizona.

"And I'm safe, you know why? He can't be, he wasn't born in this country."

The Constitution requires that a president be a natural-born US citizen.

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Trump was responding to growing criticism portraying the Tesla CEO and world's richest person as "President Musk" for the outsized role he is playing in the incoming administration.

As per ceding the presidency to Musk, Trump also assured the crowd: "No, no that's not happening."

The influence of Musk, who will serve as Trump's "efficiency czar," has become a focus point for Democratic attacks, with questions raised over how an unelected citizen with extremist views can wield so much power.

And there is even growing anger among Republicans after Musk trashed a government funding proposal this week in a blizzard of posts – many of them wildly inaccurate – to his more than 200 million followers on X.

Alongside Trump, Musk ultimately helped pressure Republicans to renege on a funding bill they had painstakingly agreed upon with Democrats, pushing the US to the brink of budgetary paralysis that would have resulted in a government shutdown just days before Christmas.

Congress ultimately reached an agreement overnight Friday to Saturday, avoiding massive halts to government services.